We propose to determine the distinct biological and chemical properites, and to pharmacologically manipulate the actions and synthesis of thromboxanes, endoperoxides, and prostaglandins in several biological systems: 1. We specifically intend to analyze the sequence of events during platelet aggregation by the simultaneous measurement of: a) formation and effect of endoperoxides, thromboxanes, and prostaglandins, b) ADP release, c) aggregation, and d) cyclic nucleotide changes. In addition with some unique pharmacological tools we plan to characterize the selectivity of responsiveness of ADP, endoperoxide, thromboxane and drug receptors on platelets. We also plan to evaluate bleeding disorders involving platelets. 2. We propose to study the biosynthesis and biological effects ofendoperoxides and thromboxanes in a) vacular smooth muscle, especially coronary arteries, b) spleen and c) lung. 3. We propose to characterize some previously unidentified endogenous (cardiac, renal and pulmonary products related to prostaglandins which have unique chemical and biological properties. 4. We propose to study the regulation of the enzymes involved in biosynthesis of thromboxanes, endoperoxides and prostaglandins.